1. Field of the Invention
The present invention relates to a method and apparatus for transmitting image data through a communication system or network.
2. Description of the Related Art
With recent advancements in color image processing technology, it has become popular to deal with a color image not only in special fields such as Computer Graphics CG design, but also in a wide variety of normal work performed in general offices. Furthermore, with advancements in communication and network technology, it has also become popular to share information through a communication system or network.
In order that an image produced at a sending end can be shared with a receiving end through a communication system or a network, it is required that the image be perceived as equal in colors at both ends.
For example, when a picture designed by a designer is sent from a sending end through communication means, and the same picture is observed at both sending and receiving ends, if there is a difference in color between the images seen at the sending and receiving ends, misinterpretation of the picture or other problems can occur.
When an image is shared by a person who produced the image and other persons who observe the image received through the Internet which has become very popular in recent years, if there is a difference between the environment or the tool employed by the person who produced the image and that employed by the persons at the receiving end, a similar problem can occur.
Such a difference in colors occurs because no information about the light source under which the image is produced and about the tool used to produce the image is not transmitted together with the image, and thus the image is processed at the receiving end on the assumption that a standard light source and a tool having standard characteristics are used at the sending end. That is, if a light source or a tool which is different from the standard light source or the standard tool is used, a difference in colors can occur between the image seen at a sending end and that seen at a receiving end.
In one known technique to solve the above problem, as shown in FIG. 8, the light source used at the sending end is guessed using a light source color guessing unit provided at either the sending or receiving end, and an image is output on an image outputting device after illumination light conversion is performed on the basis of the information about the guessed light source.
In the technique shown in FIG. 8, although it is possible to obtain information about the light source employed at the sending end, guessed by the light source guessing unit, it is still impossible to perfectly eliminate a difference arising from the difference in environmental condition because of the lack of information about the tool used to input an image and the light source and the tool used at the receiving end. In many cases, therefore, the image does not look exactly the same at both the sending and receiving ends.
If there is a difference between the light source used in the receiving-end environment in which an image is observed and that used in the sending end, the color looks different between the sending end and the receiving end because the human perception of colors depends on the light source used. Therefore, color adaptation correction is necessary. For the above reason, the process based on only information about the light source obtained by the guessing using the light source color guessing unit cannot provide an exact correction in terms of the difference in color perception due to the estimation error of the light source. Furthermore, it is impossible to correct the change in color due to the change in environmental conditions at the receiving end, and thus the colors of the image are perceived differently between the sending and receiving ends.
In view of the above problem, it is an object of the present invention to provide a simple technique of achieving better matching in terms of image colors between sending and receiving ends.
To achieve the above object, the invention provides a method and apparatus in any of aspects described below.
According to a first aspect of the invention, there is provided an image processing apparatus for transmitting image data to a second image processing apparatus having the capability of performing color adaptation conversion on the basis of output image illumination light source information and input image illumination light source information, the apparatus comprising: input means for inputting input image illumination light source information and profile information of a source device; and transferring means for transferring the input image illumination light source information, the profile information, and image data representing an input image in a form depending on the source device to the second image processing apparatus having the capability of performing color adaptation conversion through a communication line.
According to a second aspect of the present invention, there is provided an image processing apparatus comprising: inputting means for inputting input image data, profile data of a source device, and input image illumination light source information from an external apparatus through a communication line; color adaptation conversion means for performing color adaptation conversion according to output image illumination light source information and the input image illumination light source information; color matching processing means for performing a color matching process according to the profile data of the source device and profile data of an output device; and outputting means for outputting, to the output device, image data which has been subjected to the color adaptation conversion and the color matching process.
According to a third aspect of the invention, there is provided an image processing apparatus comprising: receiving means for receiving output image illumination light source information from a receiving apparatus through a communication line; inputting means for inputting input image illumination light source information; color adaptation conversion means for performing color adaptation conversion on an input image according to the input image illumination light source information and the output image illumination light source information; transmitting means for transmitting image data, which has been subjected to the color adaptation conversion, to the receiving apparatus through the communication line.